Signaling system



Nov. 7d, 1944.

M. C. GODDARD SIGNALING SYSTEM RIV l Patented Nov. 7., 1944 VSIGrNALINGrSYSTEM Myron C. Goddard, Garden City, N. Y., assignor yto Bell-TelephoneLaboratories, Incorporated,

New York, N., Y., a corporation of New York Application June 3, 1943,Serial No. 489,469

' 4 claims. (C1. 179-3) This invention relates to duplex,signaling'systems and more particularlyto 'systems of the characterdisclosed in United States Patent 1,287,831 tov Bascom in whichthreeindependent direct current duplex telegraph or signal channels and agroundvpotential compensat- ,ing channel are superimposed on a four-Wirephantom telephone group.

An object ofthe invention is to substantially re is neutralized byinductively'coupling such vchannels together in such a manner thatcross-` iire disturbance between the two telegraph conductors isneutralized by Ia simultaneous disturbance in,y an opposingdirectionduer to the inductive'coupling. i

Obviously neutralization of Crossfire, as shown in the Cory patent, canbe applied to fourfwire groups of conductors wherein eachwire is, usedlines, in accordance with present telegraph" prac! reduce, at each endof such phantomgroups the l0 for a duplex Signaling C11-Cuit andConsequently eect of crossre between the four Wires of such. balancedat' each terminal, by an Equivalent groups on the termnal relays Caueed'by in' articial line networln To obtain neutralization duetenee en deapaelty between the Wlres and by of receiving end crossre all foursignaling Awires leakage ,Welch essere effect 1S due largely to can beinductively coupled, each With'the other the proxlmlty ofthe four Wlresto each other )e three, at eachv terminal by means of a multien e' pelelmeer 'le a cable' 4 Wound transformer having one winding in seriesAnother ebteet 1ste 1'eduee mterferenee With with each wire and sendingend Crossfire `caribe eperetlen of aethe termmal relay eaueed' bysimilarly neutralized byinterconnecting the four transformer eetlenbetween a I me Wmdmg of balancing networks or articial lines, at. eachone of the teleye through Whleh Stgnalsere 'e0 terminal by a sixcondenser network, four ofthe being transmitted and the compensatingwind- Condensers being lConmcted toform a Sq'ara me et the Seme, relay'A the other two connected in the diagonals thereof A further ebteet lete reduce mterferenee Wlth and the four corners of the square'connectedto the operation of the terminal relay equipment .f the fou'r networksSuch an arrangement 'f due to longitudinal currentv induced. in the line25 neutralizing Crossi'e in a 'fourghaneltel@ 4 fireetfrem adjacentalternating entrent power graph system is known and hast beenpreviouslyv circui s. t used. However, 1n the case of systems` where Ieduplex elgnehng Systeme of' the meer ett there is a difference in groundpotential-between such as the Bascom patent above mentioned, th ttvrmn-nls, f the d lex s St m it is multiwound signaling relays foreach' of the three 30 sorlettvnesedesirbleeto cmpS-at Y eth-fdf'signaling channels are provided, one for each Te terminal of the system,each relay having one frree by empleygtg 10nedef tte fleet hdne. Wlleewindilng conecteld in series with1 its respectiv germ; nglln Blgcplentcaliliiettlwlubg signa ing c anne a second win ing connecte n f y'to a grounded balancing network having equiva- 35 ebvleu-s that Senemgend ereesre-neetrellzeftlee lent characteristics of that of thesignaling chanm Such, 9" systemq .ae prevlously deseHb-e-eby ne1 withwhich it is associated, anda third wind- Connectmg the artlvclal lmesat.east? termin?? 1 ing connected in a series circuit between groundtogether by meeee et e condenser, will. eet te', at each terminal andincluding the fourth vor (.uCe 'the dlstubmg effec? at the -t'allsmlttmgcompensating conductor and all the other third '40 end CalSed byCT'OSVSTe between any 011e 0f the windings of the signal relays at'thetwo terthreeelgnalmg W1 1`es endthegroondeempeesat' minals. whicharrangement therefore provides ing Wrewhich wlI'e 11101110165 a Wlndmg0n e.aJCh three balancing networks at each terminal, i. e., 0f theSlgnalmg Channel relayse A one for each of the three signaling ychannelsbut A feature' 0f the Presentmyentlon thefetore it wm he` notedthat thefourth or ompensat- 45 resides in baldncinefihe Compensatmg -Wlrdby ingconductor unlike the other three signaling means 0f d fOurth artlclalline 'at `each terminal conductors has no such balancir'igv network. n 3marmer eorrespondmg t0 met of the 5,153.31.

In United states Patent 1,560,540 to samud 1. Wires which requires theaddition 0f a iduiith .Coi-y, issued Novemberio, 1925, a system isdiswinding ont each of the three Signal relays at closed forneutralizing the eect of Crossfire both l5o each terminal which fourthwindings are all at the receiving end and also at thesending endconnected in series between theffourt'h' 'artificial of two groundedtelegraph circuits in which 1in@ ad'glllndl v sending end Crossfire isneutralized by connect- With .such an arrangement', condensersf can inga condenser between the articial lines of vthen beconnected'betweenthe/fourarticial Y the two duplex channels andreceiving end crossy5,5

tice, to neutralize the sending end crossre disturbance between thethree signaling wires and also between any one of the signaling wiresand the compensating wire.

Also receiving end Crossfire between any of the signaling wires and thecompensating wires can be neutralized by inductively coupling thesignaling wires and the compensating wire by means of a transformerwhereby crossre from one of the signal wires incoming at the receivingend over the compensating wire which llows through the compensatingwindings is opposed by an induced neutralizing current, due to thesignal current, which flows in an opposite direction in the fourthwindings to the Crossfire current flowing in the third or compensatingwindings.

The invention will be understood from the following description andaccompanying drawing which shows one end of two physical two-wire linesextending between distant terminals, only one being shown, and arrangedto provide three direct current duplex signaling channels and a channel'for equalizing or compensating for differences in earth potential at thetwo terminals, to which system is added means in accordance with theinvention. for neutralizing the effect of crossfire between the fourchannels on the terminal relay equipment with particular reference toneutralizingthe effect of what is known as "sending end crossflreappearing in the compensating channel due to current in any of the threesignal channelsI ReferringV to the drawing L1 and L2 represent twotwo-wire physical lines terminating in telephone equipment, not shown,as for examplein jacks as shown in the before-mentioned Bascom Patent1,287,831.

For purposes of signaling between the two terminals' 0f the lines threeduplex channels are provided comprising line conductors T1 of line L1and conductors T2 and R2. of line Lz with which channels are associatedrespective multiwound polar relays such as I, 2 and 3 at the terminalshown, and corresponding identical relays, not shown, at the distantterminal, each of which control auxiliary pulse or signal receivingrelays, also not shown.v

Windings Nos. 1 and 2 of each polar relay are the usualbalancing andline windings respectively and the No. 3 winding on each relay is theground compensating windings all of which windings (No. 3) are connectedin the usual manner ingseries between the line conductor R1 and groundat each terminal in such a manner that any K difference inA groundpotential. at the two termi.-

nals, which potential tends to effect the operation of the polar relays,wil-l be neutralized by current in an opposing direction in the No. 3 orcompensating winding of these relays as clear- `ly described intheBascompatent The method of normal operation of the system, thus farreferred to, as regards transmission of signals over the duplex channelsT1, T2, and Re,

and the compensation for differences Yin ground potential is well knownand fully described in the Bascom patent and also in a more recentPatent 2,133,832 to G; A. Pullis which patent in addition to describingmeans for providing compensation for differences in earth potential ateach terminal also describes additional means for providing fordifferences in potential between the two normally equal potential signalbatteries at the two telminals.

Crossfire neutralization' With further reference to the drawing, eacharmature of the three conventional pole-changing transmitting relays 4,5 and 6 is connected to the junction of the No. l and No. 2 windings ofthe respective polar relay in series with respective windings of a,four-winding transformer l and the connection to ground for the earthpotential compensating circuit includes the additional or fourth windingof this transformer whereby receiving end crossre between the signalingconductors and the compensating conductor is inductively neutralized asdescribed in the Cory Patent No. 1,560,540'. In addition to transformer1 which includes all three transmitting branches of the system and theground connection for the earth potential compensating channel, the twoconductors of each pair, i. re., T1 and R1 and T2 and R2 are alsoindependently coupled to each other by means of two winding transformers8 and 9 for the reason that the Crossfire between the two conductors ofeach pair may be greater than that between the conductors of differentpairs, and therefore require closer coupling.

In addition to the inductive coupling for rcceiving end Crossfire justdescribed, means for neutralizing sending end Crossfire between thesignaling channels T1, T2 and R2 and the compensating channel R1 isprovided by means of condensers IB in the manner described for twotelegraph circuits in the Cory Patent 1,560.54() which requires a linebalancing network for each channel. As previous systems of the Bascomand Pullis type, previously referred to, which require one of the fourline conductors for earth potential compensation and which have no linebalancing network, the first requirement to condition such a system forsending end Crossfire is to provide such a balancing network for thecompensating channel R1 Vin order that the condenser arrangement lll canbe interconnected in balanced relation between all four channels. Thisrequirement is accomplished bythe addition to each polar relay of afourth or No. 4 winding to balance the third or No. 3 compensatingwinding and in connection the No. 4 winding in series between ground anda fourth network NR1 corresponding to the other Athree networks NTi, NT2and NRz and simulating the line impedance of the compensating conductorR1. With this arrangement a condenser lnetwork HJ can be interconnectedbetween the four balancing networks to neutralize sending end crossre. YThe operation of this arrangement for neutral- )zing crossre at thesending end will be understood from the following. Assume that signalsare being transmitted over the first signal channel T1 by operation ofthe sending relay 4. Operation of this relay removes negative potentialfrom the relay armature and substitutes a positive' potential thereforwhich consequently causes a current to flow from right to left, asindicate-d by the solid arrow, in conductor Il, line winding 2 of relayl and line conductor T1, to negative battery and ground at the distantterminal. Operation of relay 4 also reverses the current previuslyflowing in the No. 1 balancing winding of relay l to a direction whichtends to operate the relay but this effect .is neutralized by the flowof current in windinrr 2 and hence the relay remains inert on its backcontact.

Due to capacity and mutual incluctonce 1etween the line wires thissudden potential increase 75 applied to line conductor T1 will tend tocause an impulse of crossre current in conductors R1, T2 and R2 in adirection indicated by the dotted arrows. Now assuming for example sucha crossre current owing in line conductor T2, due to through windings 2and 1 of relay 2 and balancing network NT2 to ground in a directiontendingA to operate relay 2, but due to the fact that the balancingnetwork NT1 is connected to network NT2 by means of the condensernetwork l0, a neutralizing current indicated by a wavy arrow `will flowfrom the network NT1 through the condenser network to network NT2 whichopposes crossre current in line conductor T2 which otherwise would tendto falsely operate relay 2.

Similarly, crossiire current in the compensating conductor R1 due tosignal current in conductor T1, for example, which flows to groundthrough the serially connected No. 3 windings of all three relays I, 2and 3 is neutralized 4by neutralizing current flovrnng from networkN'I'1 through the condenser network I0 to the network NR1 and thence toground through the serially connected No. 4 windings of all three relayswhich is in an opposing direction to the interfering current in the No.3 winding. y

It will therefore be noted from the foregoing that sending end crossreneutralization between all four conductors of the systems arranged forearth potential neutralization in accordance vwith the Bascom patent iseffected by providing a three independent duplex signaling channels anda ground potential compensating channel over four conductors, amultiwound polar relay at each end of and associated with each signalingchanl nel, each relay having one winding in the respective signalingchannel, a balancing winding therefor connected to a ygrounded impedancenetwork simulating the characteristics of the respective channel, and athird winding in' series with said compensating channel and ground, andmeans at each end of said channels for neutralizing the effect ofsending end crossre between any of said signaling channels and saidcompensating channel comprising a fourth winding on each relay seriallyconnected between ground and a grounded impedance network simulating thecharacteristics of said compensating conductor and a condenser networkinterconnecting all four of said impedance networks.

2. In a duplex signaling system providing three independent duplexsignaling channels and a ground potential compensating channel over fourconductors, a multiwound polar relay at each end of and associated with'each signaling channel, each relay having one winding in the respectivesignaling channel, a balancing winding therefor connected to a groundedimpedance network simulating the characteristics of the respectivechannels, and a third winding in series with said compensating channeland ground, and means at each end of said channels for neutralizing theeffect of Crossfire at both the sending and receiving ends of .thesystem between any of said signaling channels and said compensatingc-h'annel comprising a fourth winding on each relay, a groundedimpedance network simulating the characteristics of said compensatingconductor,- ysaid fourth windings being serially connected iny a circuitincluding said compensating conductor impedance network and said thirdwindings, a condenser network interconnecting all four of said impedancenetworks, and an inductive cou-` pling between the sending branches ofthe three signaling channels and the compensating channel.

3. In a multichannel duplex signaling system employing one-conductor ofa group of line wires for earth potential compensation and connected toground at each terminal in series with a third or compensating windingon each' of the duplex signalrelays at each terminal, and means at eachterminal for' neutralizing crossre between the various channels and thecompensating conductor to reduce distortion in the operation of thesignal relays, said means including an'inductive coupling between thesending branches of the signaling channels and the compensating channel,an articial line simulatingA thel impedance of the compensating linewire, a fourth winding on each duplex relay serially connected betweensaid compensating channel and said artificial line, and a condensernetwork interconnecting the articial lines of all of said line wires.

4. In a duplex composite signaling-system for groups of four conductorsto provide three separate signal channels and acompensating channel,-eachrsignaling channel employing la multiwound relay at each of itsterminals having one winding in the respective signaling channel, abalancing winding in opposition thereto, and a compensating winding, allof said compensating windings being in series with said compensatingchannel, and means for neutralizing Crossfire b'etween all fourconductors, said means including a forth winding on each of said relays.

MYRON CL'GODDARD.

